GoogleCloudPlatform · andrewsg · May 1, 2019 · Mar 28, 2019 · Mar 29, 2019 · Mar 29, 2019
diff --git a/compute/managed-instances/demo/app.py b/compute/managed-instances/demo/app.py
@@ -0,0 +1,120 @@
+# Copyright 2019, Google, Inc.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+Flask app to be used as an interactive demonstration of autohealing.
+
+Exposes a simple UI showing basic server stats and a toggle button to
+simulate a healthy/unhealthy server status for any attached health check.
+
+Attached health checks should query the '/health' path.
+"""
+
+from flask import Flask, make_response, render_template
+from re import sub
+from requests import get
+from socket import gethostname
+
+PORT_NUMBER = 80
+
+app = Flask(__name__)
+healthy = True
+
+
+@app.route('/')
+def index():
+    """Returns the demo UI."""
+    global healthy
+    return render_template('index.html',
+                           hostname=gethostname(),
+                           zone=_get_zone(),
+                           template=_get_template(),
+                           healthy=healthy)
+
+
+@app.route('/health')
+def health():
+    """Returns the simulated 'healthy'/'unhealthy' status of the server.
+
+    Returns:
+        HTTP status 200 if 'healthy', HTTP status 500 if 'unhealthy'
+    """
+    global healthy
+    template = render_template('health.html', healthy=healthy)
+    return make_response(template, 200 if healthy else 500)
+
+
+@app.route('/makeHealthy')
+def make_healthy():
+    """Sets the server to simulate a 'healthy' status."""
+    global healthy
+    healthy = True
+    template = render_template('index.html',
+                               hostname=gethostname(),
+                               zone=_get_zone(),
+                               template=_get_template(),
+                               healthy=True)
+    response = make_response(template, 302)
+    response.headers['Location'] = '/'
+    return response
+
+
+@app.route('/makeUnhealthy')
+def make_unhealthy():
+    """Sets the server to simulate an 'unhealthy' status."""
+    global healthy
+    healthy = False
+    template = render_template('index.html',
+                               hostname=gethostname(),
+                               zone=_get_zone(),
+                               template=_get_template(),
+                               healthy=False)
+    response = make_response(template, 302)
+    response.headers['Location'] = '/'
+    return response
+
+
+def _get_zone():
+    """Gets the GCE zone of this instance.
+
+    Returns:
+        str: The name of the zone if the zone was successfully determined.
+        Empty string otherwise.
+    """
+    r = get('http://metadata.google.internal/'
+            'computeMetadata/v1/instance/zone',
+            headers={'Metadata-Flavor': 'Google'})
+    if r.status_code == 200:
+        return sub(r'.+zones/(.+)', r'\1', r.text)
+    else:
+        return ''
+
+
+def _get_template():
+    """Gets the GCE instance template of this instance.
+
+    Returns:
+        str: The name of the template if the template was successfully
+        determined and this instance was built using an instance template.
+        Empty string otherwise.
+    """
+    r = get('http://metadata.google.internal/'
+            'computeMetadata/v1/instance/attributes/instance-template',
+            headers={'Metadata-Flavor': 'Google'})
+    if r.status_code == 200:
+        return sub(r'.+instanceTemplates/(.+)', r'\1', r.text)
+    else:
+        return ''
+
+
+if __name__ == "__main__":
+    app.run(debug=False, port=PORT_NUMBER)
diff --git a/compute/managed-instances/demo/requirements.txt b/compute/managed-instances/demo/requirements.txt
@@ -0,0 +1 @@
+flask==1.0
diff --git a/compute/managed-instances/demo/templates/health.html b/compute/managed-instances/demo/templates/health.html
@@ -0,0 +1,7 @@
+<div style="font-family: verdana; font-weight: bold; font-size: 40px">
+  {% if healthy %}
+  <span>HTTP/1.0 200 OK</span>
+  {% else %}
+  <span>HTTP/1.0 500 Internal Server Error</span>
+  {% endif %}
+</div>
diff --git a/compute/managed-instances/demo/templates/index.html b/compute/managed-instances/demo/templates/index.html
@@ -0,0 +1,47 @@
+<html>
+<head>
+    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0-rc.2/css/materialize.min.css">
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0-rc.2/js/materialize.min.js"></script>
+</head>
+<body>
+    <table class="striped">
+        <colgroup>
+            <col width="200">
+        </colgroup>
+        <tbody>
+            <tr>
+                <td>Hostname:</td>
+                <td><b>{{ hostname }}</b></td>
+            </tr>
+            <tr>
+                <td>Zone:</td>
+                <td><b>{{ zone }}</b></td>
+            </tr>
+            <tr>
+                <td>Template:</td>
+                <td><b>{{ template }}</b></td>
+            </tr>
+            <tr>
+                <td>Health status:</td>
+                {% if healthy %}
+                <td><span class="btn green">healthy</span></td>
+                {% else %}
+                <td><span class="btn red">unhealthy</span></td>
+                {% endif %}
+            </tr>
+            <tr>
+                <td>Actions:</td>
+                <td>
+                    {% if healthy %}
+                    <a class="btn blue" href="/makeUnhealthy">Make unhealthy</a>
+                    {% else %}
+                    <a class="btn blue" href="/makeHealthy">Make healthy</a>
+                    {% endif %}
+
+                    <a class="btn blue" href="/health">Check health</a>
+                </td>
+            </tr>
+        </tbody>
+    </table>
+</body>
+</html>